Direct actions of naringin on rat cardiac and vascular smooth muscle (Acciones directas de la naringina sobre los músculos cardíaco y liso vascular de rata)

Naringin (NRG) is a flavanone glycoside present in grapefruit juice. Its biological activity has been only partially characterized and little is known about its potential effects in the cardiovascular system. We studied the effects of NRG on the electrical and contractile activities of isolated rat hearts and on the contraction of rat abdominal aortic rings. NRG exerted a negative inotropic action in hearts with an IC50 of 72.5 µmol/L but its effects on heart rate and surface electrogram were minimal. Surprisingly, NRG (10-100 µmol/L) was able to increase tension in aortic rings contracted by isotonic KCl or phenylephrine. This action of NRG was also evident in aortic rings in basal (resting) conditions but it was absent when resting aortic rings were previously perfused with ryanodine (30 µmol/L). Our results indicate that NRG has direct actions on cardiac and vascular smooth muscles that should be taken into account when considering this molecule either as a dietetic supplement or as a template to develop therapeutic agents for human diseases.